Science: Physics: Airplanes March 22, 1999 Research: Airplanes are an efficient way of traveling to far places. Airplanes are amazing if you know what and how the air keeps the plane airborne. There are three components of flight: aerodynamics, the Bernoulli principal and supersonic flight. Some other things about flight are the four forces, lift, drag, weight, and thrust. One of the basic things you need to know about airplanes is that the places where the plane can balance on one point called the center of gravity. The tail on the plane is needed to balance the pitching movement. First of all, aerodynamics plays a major role on many things, especially in airplanes. Aerodynamics is the reaction of the air on the specially shaped wing that lifts an airplane off the ground. Also, aerodynamics is the study of gases in motion. The term aerodynamics comes from the Greeks meaning air power. Isaac Newton bases aerodynamics on the physics theorem. People who experiment with aerodynamics are called aerodynamicist. Their basic tool is the wind tunnel. A professor of engineering, Osborne Reynolds, conducted many experiments with paper airplanes and regular airplanes and found out Viscosity (thickness) affects the way fluids behave. All fluids have some viscosity. As a fluid flows over a surface, the fluid molecules closest to the surface cling microscopic roughness of the surface. As you move away from the surface, there is a small transition distance where the fluid’s viscosity limits the change in speed of the adjacent molecules, until at a certain distances the fluid is at full speed. (Paper airplane aerodynamics www.geocities.com/capecanaveral/1817/paene/html) Osborne invented a number that was devised which gives the importance of viscosity in fluid flow. It’s called the Reynold’s number. Reynold’s number =9340 for air so you’d take 9340x velocity relative to surface (mph) x length over surface fluid has traveled feet. This determines how influential the viscosity is. Secondly, Swiss mathematician and physicist, Daniel Bernoulli, created Bernoulli’s principle in 1738. It stated the concept that as the speed of a moving fluid increases, the pressure within the fluid decreases. An increase in the fluid’s speed must be matched by a decrease in pressure. The mathematical theorem for the Bernoulli affect is p + + p V2. One source said, “the principle also applies to the spinning of
a baseball” (Simons, 1989, pg. 23) The rotation causes an additional velocity component to be sent in the direction of rotation. Because of all that, the total velocity around the ball is higher on one side then the other. This is an example of how Bernoulli’s principle works. Next, supersonic flight includes speeds from mach one to five: above five are considered hypersonic. The bell X-1 rocket plane first achieved supersonic flight in 1947. “Many attempts had been made before that but when the plane ran against the sound barrier the pilot often lost control when the shock waves built up against the surface” (Compton’s 1994). Mach one is considered traveling below the speed of sound (subsonic). Mach two is traveling twice the speed of sound (supersonic). All aircraft’s that are traveling at supersonic or hypersonic speed create a shock wave that represents a big change in the air pressure. The shock is in reality a cone shape (a mach cone). The mach cone at mach 1 is more of a hill but as the mach numbers increase, the cone gets pushed back to more of a mountain. As the wave gets closer to the wing, the drag increases dramatically. When you are at subsonic mach numbers, the drag is increased as a result of small wing span or low aspect ratio. “Low aspect ratio is the ratio of span to mean chord of an airfoil” (Reithmaier, 1995). A typical supersonic airplane gives off two main shock waves: bow shock and tail shock. Next, there are four forces of flight; lift, weight, drag, and thrust. Drag is the air resistance to forward motion. Thrust is produced by the power plant that contracts drag. The formula for drag is D=1/2 x p x V2 x S x CD. The S in this formula is the area of the wing area of the whole aircraft. If the plane is level, lift will equal weight. In conclusion, airplanes have a lot of scientific information behind the way that the plane stays in the air. The airplanes have to be aerodynamically shaped to reach supersonic flight. The Bernoulli affect also helps keep the plane in the air by measuring the viscosity and comparing it to the air pressure. Supersonic flight is from mach 1 to mach 5 and above that is hypersonic. This relates to my experiment in many ways. The paper airplane has to be aerodynamically shaped so it can fly well. The paper airplane also has a Reynolds number, which was created by Daniel Bernoulli. The equation for paper airplane is 9340*10*.4 =37,000. Of course the project airplane will not be traveling at supersonic speeds but it would have the same concept of cutting through the air.